I just received mine. The DAC only outputs the left channel. Tried this on my phone, computer, and laptop with my Sennheiser 6xx and Hifiman 4xx, which work fine. Unplug the left channel and the right has zero sound at all. I think I got a lemon.

I just received mine as well and the DAC only outputs the left channel when the headphones are plugged in completely (tried on Mac, Android, and Windows). If you plug it in 3/4 of the way to where it does not "click" into place it will output to both channels however you cant move when its connected otherwise the headphone cable will fall out. Time to contact Massdrop support I suppose.

Update: MD did refund the cost of the DAC... completely no fuss.
However, despite being defective, the sound it had was nice and clean, so I took another chance on the latest drop. Just took it out of the packet and listening now... both channels are working and sounds super clean on a very sensitive IEM :)